Search

The VISTA Variables in the Via Lactea (VVV) survey obtained near-infrared photometry toward the Galactic bulge and the southern disc plane for a decade (2010 - 2019). We designed a modified Lomb-Scargle method to search for large-amplitude ($��$Ks > 1.5 mag) mid to long-term periodic variables (P > 10 d) in the 2nd version of VVV Infrared Astrometric Catalogue (VIRAC2-$��$). In total, 1520 periodic sources were discovered, including 59 candidate periodic outbursting young stellar objects (YSOs), based on the unique morphology of the phase-folded light curves, proximity to Galactic HII regions and mid-infrared colours. Five sources are spectroscopically confirmed as accreting YSOs. Both fast-rise/slow-decay and slow-rise/fast-decay periodic outbursts were found, but fast-rise/slow-decay outbursts predominate at the highest amplitudes. The multi-wavelength colour variations are consistent with a variable mass accretion process, as opposed to variable extinction. The cycles are likely to be caused by dynamical perturbations from stellar or planetary companions within the circumstellar disc. An additional search for periodic variability amongst YSO candidates in published Spitzer-based catalogues yielded a further 71 candidate periodic accretors, mostly with lower amplitudes. These resemble cases of pulsed accretion but with unusually long periods and greater regularity. The majority of other long-period variables are pulsating dusty Miras with smooth and symmetric light curves. We find that some Miras have redder $W3 - W4$ colours than previously thought, most likely due to their surface chemical compositions., 29 pages, 25 figures

The VVV survey has observed the southern disk of the Milky Way in the near infrared, covering 240 deg$^{2}$ in the $ZYJHK_S$ filters. We search the VVV Survey images in a $\sim$19 deg$^{2}$ field around $��$ Centauri, the nearest stellar system to the Sun, to look for possible overlooked companions that the baseline in time of VVV would be able to uncover. The photometric depth of our search reaches $Y\sim$19.3 mag, $J\sim$19 mag, and $K_S\sim$17 mag. This search has yielded no new companions in $��$ Centauri system, setting an upper mass limit for any unseen companion well into the brown dwarf/planetary mass regime. The apparent magnitude limits were turned into effective temperature limits, and the presence of companion objects with effective temperatures warmer than 325K can be ruled out using different state-of-the-art atmospheric models. These limits were transformed into mass limits using evolutionary models, companions with masses above 11 M$_{Jup}$ were discarded, extending the constraints recently provided in the literature up to projected distances of d, 8 pages, 6 figures, 3 tables. Accepted for publication in MNRAS

We present linear polarization observations of the exoplanet system HD 189733 made with the HIgh Precision Polarimetric Instrument (HIPPI) on the Anglo-Australian Telescope (AAT). The observations have higher precision than any previously reported for this object. They do not show the large amplitude polarization variations reported by Berdyugina et al. 2008 and Berdyugina et al. 2011. Our results are consistent with polarization data presented by Wiktorowicz et al. 2015. A formal least squares fit of a Rayleigh-Lambert model yields a polarization amplitude of 29.4 +/- 15.6 parts-per-million. We observe a background constant level of polarization of ~ 55-70 ppm, which is a little higher than expected for interstellar polarization at the distance of HD 189733., 5 pages, 1 figure, 4 tables, accepted for publication in MNRAS

Knowledge of the stellar content near the Sun is important for a broad range of topics ranging from the search for planets to the study of Milky Way structure. The most powerful method for identifying potentially nearby stars is proper motion (PM) surveys. All old optical surveys avoid, or are at least substantially incomplete, near the Galactic plane. The depth and breadth of the "Vista Variables in Via Lactea" (VVV) near-IR survey significantly improves this situation. Taking advantage of the VVV survey database, we have measured PMs in the densest regions of the MW bulge and southern plane in order to complete the census of nearby objects. We have developed a custom PM pipeline based on VVV catalogues from the Cambridge Astronomy Survey Unit (CASU), by comparing the first epoch of JHKs with the multi-epoch Ks-bands acquired later. Taking advantage of the large time baseline between the 2MASS and the VVV observations, we also obtained 2MASS-VVV PMs. We present a near-IR proper motion catalogue for the whole area of the VVV survey, which includes 3003 moving stellar sources. All of these have been visually inspected and are real PM objects. Our catalogue is in very good agreement with the proper motion data supplied in IR catalogues outside the densest zone of the MW. The majority of the PM objects in our catalogue are nearby M-dwarfs, as expected. This new database allow us to identify 57 common proper motion binary candidates, among which are two new systems within ~30pc of the Sun., 15 pages, 7 figures, accepted in the MNRAS

We report the discovery of an L dwarf companion to the A3V star �� Circini. VVV J151721.49-585131.5, or �� Cir B, was identified in a proper motion and parallax catalogue of the Vista Variables in the V��a L��ctea survey as having near infrared luminosity and colour indicative of an early L dwarf, and a proper motion and parallax consistent with that of �� Cir. The projected separation of $\sim$3.6' corresponds to $6656$ au, which is unusually wide. The most recent published estimate of the age of the primary combined with our own estimate based on newer isochrones yields an age of $370-500$ Myr. The system therefore serves as a useful benchmark at an age greater than that of the Pleiades brown dwarfs and most other young L dwarf benchmarks. We have obtained a medium resolution echelle spectrum of the companion which indicates a spectral type of L1.0$\pm$0.5 and lacks the typical signatures of low surface gravity seen in younger brown dwarfs. This suggests that signs of low surface gravity disappear from the spectra of early L dwarfs by an age of $\sim370-500$ Myr, as expected from theoretical isochrones. The mass of �� Cir B is estimated from the BHAC15 isochrones as $0.056\pm0.007$ M$_{\odot}$., Accepted for publication in the MNRAS main journal

The VISTA Variables in the Vía Láctea (VVV) survey is one of six near-infrared ESO public surveys, and is now in its fourth year of observing. Although far from being complete, the VVV survey has already delivered many results, some directly connected to the intended science goals (detection of variable stars, microlensing events, new star clusters), others concerning more exotic objects, e.g., novae. Now, at the end of the fourth observing period, and comprising roughly 50% of the proposed observations, the status of the survey, as well some of results based on the VVV data, are presented. Fil: Hempel, Maren. Pontificia Universidad Católica de Chile; Chile. The Milky Way Millennium Nucleus; Chile Fil: Minniti, Dante. Pontificia Universidad Católica de Chile; Chile. Vatican Observatory; Italia Fil: Dékány, István. Pontificia Universidad Católica de Chile; Chile Fil: Saito, Roberto K.. Pontificia Universidad Católica de Chile; Chile. Universidade Federal de Sergipe; Brasil Fil: Lucas, Philip W.. University Of Hertfordshire; Reino Unido Fil: Emerson, Jim P.. Queen Mary University of London; Reino Unido Fil: Ahumada, Andrea Veronica. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Aigrain, Suzanne. University of Exeter; Reino Unido Fil: Alonso, Maria Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina Fil: Alonso García, Javier. Pontificia Universidad Católica de Chile; Chile Fil: Amôres, Eduardo B.. Universidade de Lisboa; Portugal Fil: Angeloni, Rodolfo. Pontificia Universidad Católica de Chile; Chile Fil: Arias, Julia. Universidad de La Serena; Chile Fil: Bandyopadhyay, Reba. University of Florida; Estados Unidos Fil: Barba, Rodolfo Hector. Universidad de La Serena; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Barbuy, Beatriz. Universidade de São Paulo; Brasil Fil: Baume, Gustavo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina Fil: Beamin, Juan Carlos. Pontificia Universidad Católica de Chile; Chile Fil: Bedin, Luigi. Space Telescope Science Institute; Estados Unidos Fil: Bica, Eduardo. Universidade Federal do Rio Grande do Sul; Brasil Fil: Borissova, Jordanka. Universidad de Chile; Chile Fil: Bronfman, Leonardo. Universidad de Chile; Chile Fil: Carraro, Giovanni. European Southern Observatory; Chile Fil: Catelan, Márcio. Pontificia Universidad Católica de Chile; Chile Fil: Claria Olmedo, Juan Jose. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Contreras, Carlos. Pontificia Universidad Católica de Chile; Chile Fil: Cross, Nicholas. University of Edinburgh; Reino Unido Fil: Davis, Christopher. Joint Astronomy Centre; Estados Unidos Fil: de Grijs, Richard. Peking University; China Fil: Drew, Janet E.. University Of Hertfordshire; Reino Unido Fil: Fariña, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina Fil: Feinstein Baigorri, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina Fil: Fernandez Lajus, Eduardo Eusebio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina Fil: Folkes, Stuart. University Of Hertfordshire; Reino Unido Fil: Gamen, Roberto Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina Fil: Geisler, Douglas. Universidad de Concepción; Chile Fil: Gieren, Wolfgang. Universidad de Concepción; Chile Fil: Goldman, Bertrand. Max Planck Institute for Astronomy; Alemania Fil: González, Oscar. European Southern Observatory; Chile Fil: Gosling, Andrew. University of Oxford; Reino Unido Fil: Gunthardt, Guillermo Ivan. Universidad de La Serena; Chile Fil: Gurovich, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; Argentina Fil: Hambly, Nigel C.. University of Edinburgh; Reino Unido Fil: Hanson, Margaret. University of Cincinnati; Estados Unidos Fil: Hoare, Melvin. University of Leeds; Reino Unido Fil: Irwin, Mike J.. University of Cambridge; Reino Unido Fil: Ivanov, Valentin D.. European Southern Observatory; Chile Fil: Jordán, Andrés. Pontificia Universidad Católica de Chile; Chile Fil: Kerins, Eamonn. University of Manchester; Reino Unido Fil: Kinemuchi, Karen. National Aeronautics and Space Administration; Estados Unidos Fil: Kurtev, Radostin. Universidad de Valparaíso; Chile Fil: Longmore, Andy. University of Edinburgh; Reino Unido Fil: López Corredoira, Martin. Instituto de Astrofísica de Canarias; España Fil: Maccarone, Tom. Texas Tech University; Estados Unidos Fil: Martín, Eduardo. Instituto de Astrofísica de Canarias; España Fil: Masetti, Nicola. Instituto di Astrofisica Spaziale e Fisica Cosmica de Bologna; Italia Fil: Mennickent, Ronald E.. Universidad de Concepción; Chile Fil: Merlo, David. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina Fil: Messineo, Maria. Rochester Institute of Technology; Estados Unidos Fil: Mirabel Miquele, Igor Felix. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina Fil: Monaco, Lorenzo. European Southern Observatory; Chile Fil: Moni Bidin, Christian. Universidad Católica del Norte; Chile Fil: Morelli, Lorenzo. Università di Padova; Italia Fil: Padilla, Nelson. Pontificia Universidad Católica de Chile; Chile Fil: Palma, Tali. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; Argentina Fil: Parisi, Maria Celeste. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Parker, Quentin. Macquarie University; Australia Fil: Pavani, Daniela. Universidade Federal do Rio Grande do Sul; Brasil Fil: Pietrukowicz, Pawel. Nicolaus Copernicus Astronomical Center; Polonia Fil: Pietrzynski, Grzegorz. Imperial College London; Reino Unido Fil: Pignata, Giuliano. Universidad Andrés Bello; Chile Fil: Rejkuba, Marina. European Southern Observatory; Chile Fil: Rojas, Alejandra. Pontificia Universidad Católica de Chile; Chile Fil: Roman Lopes, Alexandre. Universidad de La Serena; Chile Fil: Ruiz, María Teresa. Universidad de Chile; Chile Fil: Sale, Stuart E.. Pontificia Universidad Católica de Chile; Chile Fil: Saviane, Ivo. European Southern Observatory; Chile Fil: Schreiber, Matthias R.. Universidad de Valparaíso; Chile Fil: Schröder, Anja C.. Hartebeesthoek Radio Astronomy Observatory; Sudáfrica Fil: Sharma, Saurabh. Universidad de Valparaíso; Chile Fil: Smith, Michael. University Of Kent; Reino Unido Fil: Sodré Jr., Laerte. Universidade de Sao Paulo; Brasil Fil: Soto, Mario. Universidad de La Serena; Chile Fil: Stephens, Andrew W.. National Astronomical Observatory of Japan; Japón Fil: Tamura, Motohide. Gemini Observatory; Estados Unidos Fil: Tappert, Claus. Universidad de Valparaíso; Chile Fil: Thompson, Mark A.. University Of Hertfordshire; Reino Unido Fil: Toledo, Ignacio. ALMA Observatory; Chile Fil: Valenti, Elena. European Southern Observatory; Chile Fil: Vanzi, Leonardo. Pontificia Universidad Católica de Chile; Chile Fil: Weidmann, Walter Alfredo. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Zoccali, Manuela. Pontificia Universidad Católica de Chile; Chile

We report the discovery of 76 new T dwarfs from the UKIDSS Large Area Survey (LAS). Near-infrared broad and narrow-band photometry and spectroscopy are presented for the new objects, along with WISE and warm-Spitzer photometry. Proper motions for 128 UKIDSS T dwarfs are presented from a new two epoch LAS proper motion catalogue. We use these motions to identify two new benchmark systems: LHS 6176AB, a T8+M4 pair and HD118865AB, a T5.5+F8 pair. Using age constraints from the primaries and evolutionary models to constrain the radii we have estimated their physical properties from their bolometric luminosity. We compare the colours and properties of known benchmark T dwarfs to the latest model atmospheres and draw two principal conclusions. Firstly, it appears that the H - [4.5] and J - W2 colours are more sensitive to metallicity than has previously been recognised, such that differences in metallicity may dominate over differences in Teff when considering relative properties of cool objects using these colours. Secondly, the previously noted apparent dominance of young objects in the late-T dwarf sample is no longer apparent when using the new model grids and the expanded sample of late-T dwarfs and benchmarks. This is supported by the apparently similar distribution of late-T dwarfs and earlier-type T dwarfs on reduced proper motion diagrams that we present. Finally, we present updated space densities for the late-T dwarfs, and compare our values to simulation predictions and those from WISE., Comment: MNRAS accepted. Updated 9th May 2013 to correct error in column headings for Table 4

Vista Variables in the Via Lactea (VVV) is an ESO Public Survey that is performing a variability survey of the Galactic bulge and part of the inner disk using ESO's Visible and Infrared Survey Telescope for Astronomy (VISTA). The survey covers 520 deg^2 of sky area in the ZYJHK_S filters, for a total observing time of 1929 hours, including ~ 10^9 point sources and an estimated ~ 10^6 variable stars. Here we describe the current status of the VVV Survey, in addition to a variety of new results based on VVV data, including light curves for variable stars, newly discovered globular clusters, open clusters, and associations. A set of reddening-free indices based on the ZYJHK_S system is also introduced. Finally, we provide an overview of the VVV Templates Project, whose main goal is to derive well-defined light curve templates in the near-IR, for the automated classification of VVV light curves., Comment: 25 pages, 18 figures. To appear in the Carnegie Observatories Astrophysics Series, Volume 5

We investigate the old star clusters in the sample of cluster candidates from Froebrich, Scholz & Raftery 2007 -- the FSR list. Based on photometry from the 2-Micron All Sky Survey we generated decontaminated colour-magnitude and colour-colour diagrams to select a sample of 269 old stellar clusters. This sample contains 63 known globular clusters, 174 known open clusters and 32 so far unclassified objects. Isochrone fitting has been used to homogeneously calculate the age, distance and reddening to all clusters. The mean age of the open clusters in our sample is 1Gyr. The positions of these clusters in the Galactic Plane show that 80% of open clusters older than 1Gyr have a Galactocentric distance of more than 7kpc. The scale height for the old open clusters above the Plane is 375pc, more than three times as large as the 115pc which we obtain for the younger open clusters in our sample. We find that the mean optical extinction towards the open clusters in the disk of the Galaxy is 0.70mag/kpc. The FSR sample has a strong selection bias towards objects with an apparent core radius of 30" to 50" and there is an unexplained paucity of old open clusters in the Galactic Longitude range of 120deg < l < 180deg., 11 pages, 6 figures, 1 table, accepted for publication by MNRAS, a complete version with the complete table and all figures can be found at http://astro.kent.ac.uk/~df/

We report the discovery of 47 new T dwarfs in the Fourth Data Release (DR4) from the Large Area Survey (LAS) of the UKIRT Infrared Deep Sky Survey with spectral types ranging from T0 to T8.5. These bring the total sample of LAS T dwarfs to 80 as of DR4. In assigning spectral types to our objects we have identified 8 new spectrally peculiar objects, and divide 7 of them into two classes. H2O-H-early have a H2O-H index that differs with the H2O-J index by at least 2 sub-types. CH4-J-early have a CH4-J index that disagrees with the H20-J index by at least 2 subtypes. We have ruled out binarity as a sole explanation for both types of peculiarity, and suggest that they may represent hitherto unrecognised tracers of composition and/or gravity. Clear trends in z'(AB)-J and Y-J are apparent for our sample, consistent with weakening absorption in the red wing of the KI line at 0.77microns with decreasing effective temperature. We have used our sample to estimate space densities for T6-T9 dwarfs. By comparing our sample to Monte-Carlo simulations of field T dwarfs for various mass functions of the form phi(M) \propto M^-alpha, we have placed weak constraints on the form of the field mass function. Our analysis suggests that the substellar mass function is declining at lower masses, with negative values of alpha preferred. This is at odds with results for young clusters that have been generally found to have alpha > 0., 23 pages, 10 figures. MNRAS accepted. Version 2 includes omitted authors.

We present a deep circular polarization image of the Orion BN/KL nebula in the Ks band and correlations of circular polarization, linear polarization, and H-Ks color representing extinction. The image of circular polarization clearly reveals the quadrupolar structure around the massive star IRc2, rather than BN. H-Ks color is well correlated with circular polarization. A simple relation between dichroic extinction, color excess, circular and linear polarization is derived. The observed correlation between the Stokes parameters and the color excess agrees with the derived relation, and suggests a major contribution of dichroic extinction to the production of circular polarization in this region, indicating the wide existence of aligned grains., Comment: 15 pages, 3 figures, accepted for publication in The Astrophysical Journal Letters

The masses and temperatures of young low mass stars and brown dwarfs in star- forming regions are not yet well established because of uncertainties in the age of individual objects and the spectral type vs. temperature scale appropriate for objects with ages of only a few Myr. Using multi-object optical spectroscopy, 45 low-mass stars and brown dwarfs in the Trapezium Cluster in Orion have been classified and 44 of these confirmed as bona fide cluster members. The spectral types obtained have been converted to effective temperatures using a temperature scale intermediate between those of dwarfs and giants, which is suitable for young pre-main sequence objects. The objects have been placed on an H-R diagram overlaid with theoretical isochrones. The low mass stars and the higher mass substellar objects are found to be clustered around the 1 Myr isochrone, while many of the lower mass substellar objects are located well above this isochrone. An average age of 1 Myr is found for the majority of the objects. Assuming coevality of the sources and an average age of 1 Myr, the masses of the objects have been estimated and range from 0.018 to 0.44Msun. The spectra also allow an investigation of the surface gravity of the objects by measurement of the sodium doublet equivalent width. With one possible exception, all objects have low gravities, in line with young ages, and the Na indices for the Trapezium objects lie systematically below those of young stars and brown dwarfs in Chamaeleon, suggesting that the 820 nm Na index may provide a sensitive means of estimating ages in young clusters., Comment: 19 pages, accepted by MNRAS

The Vista Variables in the V\'ia L\'actea (VVV) ESO Public Survey is an ongoing time-series, near-infrared (IR) survey of the Galactic bulge and an adjacent portion of the inner disk, covering 562 square degrees of the sky, using ESO's VISTA telescope. The survey has provided superb multi-color photometry in 5 broadband filters ($Z$, $Y$, $J$, $H$, and $K_s$), leading to the best map of the inner Milky Way ever obtained, particularly in the near-IR. The main variability part of the survey, which is focused on $K_s$-band observations, is currently underway, with bulge fields having been observed between 31 and 70 times, and disk fields between 17 and 36 times. When the survey is complete, bulge (disk) fields will have been observed up to a total of 100 (60) times, providing unprecedented depth and time coverage. Here we provide a first overview of stellar variability in the VVV data, including examples of the light curves that have been collected thus far, scientific applications, and our efforts towards the automated classification of VVV light curves., Comment: Presented at the "40 Years of Variable Stars: A Celebration of Contributions by Horace A. Smith" conference (arXiv:1310.0149). 49 pages, 28 figures